The present invention relates to a new position, speed and direction detector. More specifically, the present invention relates to a device for monitoring and identification of the absolute position, speed and direction between two elements that are in relative rotating or linear movement.
The device features as main characteristic thereof a low-cost device that allows the accurate identification of the above mentioned parameters.
As is known to those skilled in the art, the conventional systems employ optical or electromagnetic absolute position detectors to measure and control parameters, such as resolvers or encoders.
However, all of those devices have the drawback of high device cost, associated to the need of complex and expensive electronic circuits for interpretation of the signals provided by those devices.
Another drawback of those conventional systems is that they do not possess the necessary sturdiness for heavy duty service.
Accordingly, it is an object of the present invention to provide a low-cost position, speed and direction detector that does not require complex and expensive control circuits.
It is another object of the present invention to provide a low-cost position, speed and direction detector having a simple and sturdy construction.
It is yet another object of the present invention to provide a particular device that can be easily incorporated into electrical machines, so as to ensure accuracy, sturdiness and easy maintenance, the application thereof in electrical machines being particularly simplified in some cases, due to the fact of employing the machine""s geometrical configuration, more specifically the arrangement of the rotor teeth or poles.
These and other objects and advantages of the present invention are achieved with a device that detects the position, speed and direction between two elements in relative movement to each other, by monitoring and controlling the magnetic permeability measured by the device.
This device is comprised of at least a pair of polar search elements attached to one of the parts, and a continuous reference element attached to the other part.
The pair of polar search elements is constituted by cores comprised of ferromagnetic sheets having at least two longitudinal teeth arranged on its face turned to the continuous reference elements and surrounded by drive coils.
The polar elements are constructed in such a manner that the width of and spacing between its teeth are exactly equal to the width of and spacing between the teeth of the continuous reference element.
The polar elements are totally electrically and magnetically uncoupled but are mechanically coupled to each other, in such a manner that, when the centerlines of the teeth of a polar element are fully aligned with the centerline of the teeth of the continuous reference element, the other polar element will have the centerline of its teeth displaced by exactly half a tooth width from the centerline of the continuous reference element tooth.
Each polar search element is surrounded by a winding comprised of at least one drive coil.
The drive coil is individually fed by a pre-established, high frequency current source that generates a magnetic field. The voltage generated in this coil is a function of the permeability measured by the polar search element.
In the event that more than one coil is employed, the coil not fed by the current source is employed as reading coil, the generated voltage of which is a function of the permeability measured by the polar search element.
The above mentioned continuous reference element is an integral part of the machine and is in turn provided with a core comprised of ferromagnetic sheets with longitudinal teeth uniformly distributed along its face turned to the pair of polar elements.
The distance between the teeth of the continuous reference element should be about 2-2.5 times the teeth width.
After the reference element is attached to one of the moving parts, the pair of polar elements is attached to the other part, preferably the static part, so that when one of the polar elements has the centerlines of its teeth fully aligned with the centerline of the continuous reference element teeth, the other polar element should have the centerline of its teeth displaced by exactly half a tooth width in relation to the centerline of the continuous reference element teeth.